1. Field of the Invention
This invention relates generally to perpendicular magnetic recording data storage systems, and more particularly to a system that uses a medium with a recording layer formed over a “soft” or relatively low-coercivity magnetically permeable underlayer, and a recording head with a single write pole and a trailing shield.
2. Description of the Related Art
Perpendicular magnetic recording, wherein the recorded bits are stored in a perpendicular or out-of-plane orientation in the recording layer, is a promising path toward ultra-high recording densities in data storage systems, such as hard disk drives (HDDs). One type of system uses a recording head with a single write pole (WP) and a “dual-layer” recording disk with the perpendicular magnetic data recording layer (RL) formed over a “soft” or relatively low-coercivity magnetically permeable underlayer (SUL). The SUL serves as a return path for magnetic flux from the WP back to the recording head's return pole (RP). However, this type of system also results in the write field inside the RL being oriented nearly normal to the surface of the RL, i.e., along the perpendicular easy axis of magnetization of the RL. This nearly parallel alignment of the write field with the RL easy axis has the disadvantage that relatively high write fields are necessary to reverse the magnetization in the RL. To address this problem, the recording head may have a trailing shield (TS) of magnetically permeable material spaced down-track from the WP and separated from the WP by a trailing gap of nonmagnetic material. The TS slightly alters the angle of the write field and makes writing easier.
It can be difficult and costly to manufacture large numbers of these types of perpendicular magnetic recording HDDs. The disk requires a relatively thick SUL to avoid magnetic saturation, which requires additional material and increases the manufacturing time and cost. Also, to increase the disk data storage density the width of the WP will need to decrease to decrease the width of the data tracks. This will require a recording head with a relatively thin TS with tight tolerances to increase the write field, which makes high-yield manufacturing difficult.
What is needed is a perpendicular magnetic recording system that is less difficult and costly to manufacture in large numbers, but still uses a recording head with a TS to improve the writing process.